Tuesday, December 9, 2008

Shimano M970 XTR Crankset Installation

After a long trip on the bus from office to Tay Junction at Bukit Timah this evening, I finally got hold of the Shimano tools required to install my Shimano M970 XTR crankset that was shipped from Chain Reaction Cycles last weekend. The main tool required is the TL-FC35 which is a crank arm screw. The TL-FC17 Adjustment Nut assists in tightening the adjustment ring. I didn't buy the TL-FC32 because I already have the Park Tool BBT-9 bottom bracket tool.

Shimano M970 XTR crankset (with TL-FC35 crank arm screw and TL-FC17 Adjustment Nut on bottom left).

I started the migration operation immediately upon reaching home. Took off the Shimano M762 XT crankset from my bike after a little bit of fiddling (lucky I still have the instruction sheet). It took about 30 minutes. After which I realised that I should have spend the $20 to buy the TL-FC32 bottom bracket tool because the wrench ring has an open end which would make it much easier to slide into the bottom bracket adapters. P1070184_editRemoving the left bottom bracket adapter of my bike encountered a little difficulty because the Brain inertia valve cable was tightly run against the side of the adapter ring. The Park Tool BBT-9 bottom bracket tool ring was a complete circle and the rims are rather wide too. I couldn't slide the bottom bracket tool onto the adapter without removing the Brain inertia valve from its bracket on the chain stay in order to give some slack to the cable. This was the scary part as I reckoned the Brain Fade system will be very costly if it is damaged due to some dumb accident. If I bought the Shimano TL-FC32 bottom bracket tool which has an open end, I would imagine that I wouldn't have to go through the hassle of fiddling with the Brain inertia valve in the first place.

Removed the existing Shimano M762 XT crankset (custom for Specialized but basically similar to Shimano M770 Deore XT crankset).

Installing the XTR crankset took about 1 hour reading the instruction sheet supplemented with the Park Tool Big Blue Book of Bicycle Repairs (2nd Edition). Despite reading and re-reading the Shimano Technical Service Instructions sheet, I still managed to skip something in step 1 and had to retract the step again. Basically I inserted the right crank unit after installing the right adapter. The correct procedure for step 1 was to complete the installation of both left and right adapters before inserting the right crank arm unit. Does it matter? I don't know but it's best to follow the steps! Another part that delayed my task was my doubts on why there is a play or gap in the shaft (between the crank arm and left adapter) after putting on the left crank arm. I took off the crank arm again as I was having doubts as to whether I have done it right. Then I came to realise that tightening the crank arm fixing bolt will reduce the play as it forces the crank arm deeper into the shaft serrations; and after tightening the bolt is to turn the adjustment nut to remove the remaining amount of play. This realisation is thanks to page 80 of the Park Tool Big Blue Book of Bicycle Repairs!

Completed the task!

Personally, I find the design for the mounting mechanism of the Shimano M970 XTR crankset to be a little cranky in terms of the special tools required and that it is quite different from its XT or LX cousins. Perhaps this is how Shimano manages to shave more weight in the XTR version. Throughout this process, I found the usefulness and ease with which the Park Tool P-Handle hex wrenches helped me in speeding up the tightening and loosening of bolts.

A closer look at this engineering piece of art.

Finally, I brought the bike down for a test spin around my neighbourhood including the changing of gears. Everything was operating perfectly. Perhaps because the crank arms of this crankset that I purchased is 170mm instead of the usual 175mm, I could feel the spin to be smoother. Or maybe because they are new and freshly greased. All-in-all, it was a nice experience as this is the first time I am installing a crankset on my own. And it's an XTR!

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  1. Hey, what do i need to remove the Shimano M762 XT crankset? Can you give me a few pointers on how to remove it?

    My cranks are creaking and I want to take them off and clean them.

    My seat creaks every few months, and i take it out and clean the seat post and the creaking stops. Weird - but i'm getting the same creak from the cranks now.

  2. Hi "dot",

    Likely either you own a Specialized bike else you bought this crankset from resale market. The Shimano M762 XT is custom for Specialized brand bikes but that's beside the point, fact is, it's exactly same in operation and maintenance as with the Shimano M770 XT. So, look for the FC-M770 product manual at the Shimano website. But anyway, here's the Shimano FC-M770 link page.

    In the above link page, there are PDF links to the tech docs and parts blow out diagram. Download and print the "SI-1J10A-002" manual. A bit of warning: the manual is very compact and "cranky" to work with. Make sure you read it carefully first before commencing your tasks. The only special tool you'll need is the Shimano TL-FC32 to both install/remove the crank unit. The Park Tool BBT-19 does the same. Meaning to say, both tools are compatible with the Shimano Hollowtech II external bearing BB cup.

    You've also requested for cleaning tips. Short of writing an unnecessary thesis in this commentary, I think the Instructables website does well with the step-by-step guide.

    Instructables: Stop Creeky Cranks

    Hope you found these useful.